Electromagnetic Induction

Question 7 • (OC27) Earth/Space Sci-2001310-S2-Nelson

Which description correctly summarizes how an electric motor causes an axle to turn?

Answer

Force generated through the brushes rotates the commutators. They then generate a force that rotates the armature to spin until the like poles of the electromagnet and the permanent magnet align and motion stops.

The poles of the magnetic field generated around the armature are attracted to the opposite poles of the permanent magnet. As the opposite poles align, the commutator reverses the current direction so like poles are aligned and the armature continues to spin.

The poles of the magnetic field generated around the armature are attracted to the like poles of the permanent magnet. This causes the armature to spin and the electricity within the armature to flow back through the circuit to the battery.

Explanation

Current in the armature creates magnetic poles, and opposite poles attract, producing a turning force. As the armature turns and its poles approach alignment with the permanent magnet’s opposite poles, the commutator reverses the current, switching the armature’s poles. This keeps the magnetic force turning the armature and axle, as described in choice B.

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